* lib/screenshooter-utils.h: add define for default application.
  * lib/screenshooter-utils.c:
    - (screenshooter_read_rc_file) read the default application.
    - (screenshooter_write_rc_file) write the default application.
    - (screenshooter_open_screenshot) only open if app != "none".
  * lib/screenshooter-dialogs.c:
    - add a define for icon size.
    - (set_default_item) added to select the correct item of the combobox when
      displaying the interface.
    - (add_item) use the icon size define.
    - (populate_liststore) add the "none" item on the top of the liststore.
    - (screenshooter_dialog_new) add a call to set_default_item.


(Old svn revision: 5937)